How much sensitivity on MW?

How much sensitivity on MW?

Post by Chris Do » Thu, 24 Aug 2000 04:00:00

Hello,

Since everyone seems to be talking MW, I have a general question. How
much sensitivity is really needed or wanted on MW? For instance, when you
look at the MW figures on a lot of communications receivers, there is
deliberate attenuation. I understand that this is to avoid MW bleed
through on SW, and that a lot of users defeat this attenuation. Is it
really necessary to do that given the typical noise level on the MW band
in an urban area? What is the real world difference between 50uV
sensitivity on MW and 1uV? Everyone seems to talk sensitivity, and I'm
wondering how much is enough...

Chris VE6RDC

 
 
 

How much sensitivity on MW?

Post by Peter Mau » Fri, 25 Aug 2000 09:20:52



> Hello,

> Since everyone seems to be talking MW, I have a general question. How
> much sensitivity is really needed or wanted on MW? For instance, when you
> look at the MW figures on a lot of communications receivers, there is
> deliberate attenuation. I understand that this is to avoid MW bleed
> through on SW, and that a lot of users defeat this attenuation. Is it
> really necessary to do that given the typical noise level on the MW band
> in an urban area? What is the real world difference between 50uV
> sensitivity on MW and 1uV? Everyone seems to talk sensitivity, and I'm
> wondering how much is enough...

  Most SW receivers have more sensitivity than they need. 1uv is
more than enough. Limiting factors to successful capture of HF
signals include atmospherics which are the lion's share of the
limitation. Extra sensitivity won't help.

  On MW, however, city grade signals are hundreds of times more
powerful than the a strong SW signal on the same antenna, on the
same radio. And overload of the front end is possible. Attenuation
really makes sense there, especially if you have a local MW station
nearby. Overload at the front end can create artifacts all over the
dial, and well into HF, depending on receiver design.

  However, some listeners, do not have local RF to contend with. And
the additional sensitivity achieved by removing the attenuation, can
materially quiet a receiver during listening. Noise on MW in Urban
areas can indeed by high, and reducing the attenuation, within
limits, can improve quieting considerably.

  In my listening area, near Grayslake, IL, I can receive WLS fine
with my antenna/receiver combinations. But only on those receivers
without MW attenuation, is WLS actually quiet.

   An improvement from 50uV to 1uV in sensitivity, is like moving 45
miles closer to the transmitter.

   But you may suffer on other areas of the band as a result.

Quote:

> Chris VE6RDC

 
 
 

How much sensitivity on MW?

Post by garyarn.. » Fri, 25 Aug 2000 11:00:13



Quote:> Hello,

> Since everyone seems to be talking MW, I have a general question. How
> much sensitivity is really needed or wanted on MW? For instance, when
you
> look at the MW figures on a lot of communications receivers, there is
> deliberate attenuation. I understand that this is to avoid MW bleed
> through on SW, and that a lot of users defeat this attenuation. Is it
> really necessary to do that given the typical noise level on the MW
band
> in an urban area? What is the real world difference between 50uV
> sensitivity on MW and 1uV? Everyone seems to talk sensitivity, and I'm
> wondering how much is enough...

> Chris VE6RDC

According to the White Paper, MW sensitivity on the Grundig Sat 800 is
slightly better than on SW -- much less than 1uV.  On my Sat 800, I
notice I can get KFRC - San Francisco - 610, about 200 miles from me,
day and night, MUCH stronger and cleaner with less noise than on my
CCRadio.  Both radios using internal ferrite bar antenna.
--
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How much sensitivity on MW?

Post by AC6V » Fri, 25 Aug 2000 04:00:00




> > Hello,

> > Since everyone seems to be talking MW, I have a general question. How
> > much sensitivity is really needed or wanted on MW?

SNIP

Quote:

> > Chris VE6RDC

=========
Take a look at ON4UN's Book "Low Band DXing. He discusses "maximum useable
sensitivity" to wit:
"Maximum useable receiver sensitivity on the low bands is limited by the
atmospheric noise plus man made noise"

Great reference book. It is ISBN 0-87259-704-0 ARRL Order No. 7040

--
73 From Rod In Oceanside, CA
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